I hope what I will do is correct to put it here.
I updated today iputils and suddenly I couldn't connect to my networks anymore.
I'm not an expert and I don't know exactly what was going on.
1) I tried to connect using netcfg to wireless with WPA security, and the result was dhcp lease attempt failed.
2) I tried to connect using netcfg to ethernet, same problem as before.
3) I used dhcp without netcfg and it connected correctly.
then I downgraded iputils and netcfg worked again.